Presently, fusion welding is a widely used technique for welding together small, metal components. Fusion welding is achieved by bringing two components together. One of the components is formed with a small nib or projection, which contacts the other. This creates a small, spot contact having a relatively high resistance. An electric charge from a bank of capacitors is then discharged between the two components. The energy of the electric charge is dissipated at the point contact, resulting in local melting of the two metals. The melted zones fuse together, to weld the two components together. The welding is extremely quick and only causes heating and melting of small areas of each component. Consequently, by careful control of the electric charge and other operating conditions, relatively small components can be welded together.
Commonly, fusion welding is used to mount a variety of studs or posts in position, which may have plain shafts, threaded shafts or shafts of a special configuration. It is also used to weld jewelry components together. One particular application involves the welding of posts or studs for earrings to small plates that hold the ornamental part of the earring.
In such an application, and in many similar applications, the post or pin is relatively small and difficult to handle. Further, it is desirable that these components be produced at a relatively high speed, in large quantities. However, if each of the two components has to be manually inserted into the fusion welding machine, then the operation is of necessity relatively slow. It is desirable that the operation should be automated as much as possible.
Proposals have been made for automating the feed of the pins or posts to a fusion welding machine, more particularly the supply of small pins for jewellery and the like. However, earlier proposals have not been entirely satisfactory, and tend to suffer from a number of disadvantages.
In one known automatic machine, pins are fed by an air flow through a flexible tube. This tube is connected to a rigid tube running through a piston rod of the drive cylinder. Since the flexible tube does not extend right down to the electrode holder at the bottom of the drive cylinder, difficulties occur with the feed of the pins through the rigid tube. Frequently, the pins become jammed, with two or more pins becoming wedged side by side.
The actual electrode holder itself is a power-operated electrode holder and has a moveable jaw that is operated by an air piston and cylinder assembly. This drives the moveable jaw against a fixed jaw, to hold a pin in position.
Experience with such a device suggests that it is unreliable. Jamming of the pins or posts in the feed path is a frequent occurrence.